From January 1994 to July 1996 we immunized metastatic melanoma patients with HLA-A2-compatible, interleukin-2 (IL-2)-secreting, immunogenic melanoma lines in an attempt to induce a systemic reaction that might also affect distant melanoma lesions. Twelve patients (6 male and 6 female) aged from 28 to 72 years, affected with visceral and/or subcutaneous (s.c.) melanoma metastases, were treated. Two different HLA-A2⁺ melanoma lines were transduced with the human IL-2 gene (14932/IL-2 and 1B6/IL-2) and used as vaccine. Two groups of 4 patients each were injected s.c. with 5×10⁷ and 15×10⁷ irradiated 14932/IL-2 melanoma cells respectively, whereas a third group received 5×10⁷ cells of the second line (1B6/IL-2). All patients received the vaccine on days 1, 13, 26; if no progression was evident, further immunizations were administered at monthly intervals. All patients were assessable for clinical response after at least three injections of the vaccine. In 4 cases a stabilization of disease lasting from 2 to 6 months was observed; in 2 of them a mixed type of response to treatment was noted with simultaneous evidence of regressing and non-responding lesions in the same patients. No signs of clinical response were found in the remaining patients. Nine patients died of disease between 3 and 24 months after the onset of therapy, whereas 3 were alive 3 months after the end of therapy. The local and systemic side-effects of treatment were mild. These results indicate that vaccination with cells bearing the appropriate antigens and releasing IL-2 locally can produce weak clinical responses, but also indicate that better results may be achieved through modifications of the vaccine, the schedule of immunization and/or a more appropriate selection of patients.